Why is our rudder so heavy?

[RogerFoxTerrier]

The rudder for our 19874 FoxTerrier 22 is really heavy - not weighed it, but I'd say it's somewhere between 30 and 40kg.

Why? I know a rudder has to be strong, but was it just the way they were built back then?

I'm wondering how hard it would be to fabricate a lighter one with ply and GRP...

 

[AntarcticPilot]

Is it hollow? If so it may have filled with water.

 

[RogerFoxTerrier]

Is it hollow? If so it may have filled with water.

No, It's solid.

 

[Chiara’s slave]

The loads are considerable. Personally, I would not replace a functional factory rudder with a home built one, unless you’re qualified/experienced.

 

[KevinV]

By the shape of it that rudder looks like it's made from ply already - probably really good quality stuff if it's lasted this long. The weight doesn't affect you one bit once it's on the boat, I'd leave well alone.

FWIW, mine's fibreglass in two halves and weighs about 30kg too (more when the core was waterlogged!) - same size boat.

 

[Hoolie]

We have a similar, but a lot larger, solid rudder. It has at times been subject to impact so personally I wouldn't dream of replacing it with something less robust!

 

[Snowgoose-1]

If it's a lift keel version , the rudder will have to be bigger. The Anderson 22 is a lift keel and has a wooden rudder which is quite heavy. Yours may be like this.

 

[Seven Spades]

I wonder if it is made from Lignum Vite, if so you can sell it on eBay and buy a new rudder and pocket the change.

 

[RogerFoxTerrier]

If it's a lift keel version , the rudder will have to be bigger. The Anderson 22 is a lift keel and has a wooden rudder which is quite heavy. Yours may be like this.

Yes it's a lift keel.

I'll leave it alone, but thanks all, I've learnt a lot from that!

 

[KompetentKrew]

When removing my rudder I lowered it onto an upturned bucket, which it immediately crushed.

 

[Chiara’s slave]

When removing my rudder I lowered it onto an upturned bucket, which it immediately crushed.

Not unusual. Even our blade is pretty heavy. Its like a big dinghy rudder, pivoting blade in a stainless stock, but still weighs a lot. Many other parts are clearly built for lightness, but the foils are built for strength.

 

[billskip]

The rudder for our 19874 FoxTerrier 22 is really heavy - not weighed it, but I'd say it's somewhere between 30 and 40kg.

Why? I know a rudder has to be strong, but was it just the way they were built back then?

I'm wondering how hard it would be to fabricate a lighter one with ply and GRP...
View attachment 192070

It has to be heavier than it's displacement

 

[Chiara’s slave]

It has to be heavier than it's displacement

I don’t think that is so. It might help, if it were to be hung on pintles with no means of retention apart from gravity, but that would surely be the height of foolishness. Ours is definitely heavier than water, but as it’s held down by a powerful downhaul system, it wouldn’t matter if it wasn’t. I think it’s built around a thick stainless web, and has a lot of grp making up its solid shape. All for strength, not to make it sink. A simple transom hung rudder could be bolted or pinned onto it's pintles, no need to be heavy apart from it's need for stiffness and strength.

 

[billskip]

I don’t think that is so. It might help, if it were to be hung on pintles with no means of retention apart from gravity, but that would surely be the height of foolishness. Ours is definitely heavier than water, but as it’s held down by a powerful downhaul system, it wouldn’t matter if it wasn’t. I think it’s built around a thick stainless web, and has a lot of grp making up its solid shape. All for strength, not to make it sink. A simple transom hung rudder could be bolted or pinned onto it's pintles, no need to be heavy apart from it's need for stiffness and strength.

I was thinking more on the lines of buoyancy, "trying to float" will surly attempt increase the heel angle, or create instability when heeled in a heavy sea.

 

[Chiara’s slave]

I was thinking more on the lines of buoyancy, "trying to float" will surly attempt increase the heel angle, or create instability when heeled in a heavy sea.

A question of scale. 10kg of buoyancy against a ton of boat? And that would be a big fat and light rudder.

 

[Rum Run]

The rudder on my Anderson 22 is similar in shape to the OP's picture and is solid iroko so not light at all. Possibly this one is also Iroko.
I had considered making a composite one, using closed cell foam and carbon fibre cloth, designed on the principle of trying to maintain strength but reducing weight. It started to look expensive!
Normal plywood has half the veneers going in a direction the does not help stiffness in a rudder, also it sucks water into the end grain and rots fast, plus is not low density so still heavy.
Maybe a lower density wood (spruce perhaps), with hardwood leading and trailing edges, all sheathed in glass cloth would be sufficient. Probably one of Gougeon Brothers technical guides has a scheme.

 

[Snowgoose-1]

The rudder on my Anderson 22 is similar in shape to the OP's picture and is solid iroko so not light at all. Possibly this one is also Iroko.
I had considered making a composite one, using closed cell foam and carbon fibre cloth, designed on the principle of trying to maintain strength but reducing weight. It started to look expensive!
Normal plywood has half the veneers going in a direction the does not help stiffness in a rudder, also it sucks water into the end grain and rots fast, plus is not low density so still heavy.
Maybe a lower density wood (spruce perhaps), with hardwood leading and trailing edges, all sheathed in glass cloth would be sufficient. Probably one of Gougeon Brothers technical guides has a scheme.

It might be fun using 3d printing for a new
rudder and then fill it with a material of choice
I would guess that most conventional rudders would sink if you took them off the boat .

 

[Chiara’s slave]

It might be fun using 3d printing for a new
rudder and then fill it with a material of choice
I would guess that most conventional rudders would sink if you took them off the boat .

I can assure you its not much fun when they break

 

[billskip]

A question of scale. 10kg of buoyancy against a ton of boat? And that would be a big fat and light rudder.

I'm not arguing your point, however 10 kg of buoyancy is quite a lot when you are trying to sink it with a fulcrum point well above the centre line..
I would sooner have the weight working for me.

 

[Mister E]

Would the weight help to reduce flutter at certain angles in some conditions?